The present invention relates to low-fat spreads; particularly, to spreads suitable as low-calorie substitutes for butter and margarine, and to a process for preparing them.
Low-fat spreads are recognized as those having from 30% to less than 80% fat content. Typically, they are water-in-oil emulsions. Low-fat spreads suitable for use as margarine substitutes are required to have certain flow or spread characteristics and should resist free oil or free water separation. And, they should otherwise simulate the characteristics of butter and margarine, including rapid melt on the tongue, good mouthfeel, fairly shiny appearance, good stability to heat such as when spread on hot foods, and freeze/thaw stability.
Among the most desirable low-fat spreads are those which offer a significant fat and calorie reduction as compared to conventional margarine or butter. Diet margarines are generally recognized as having less than half of the normal fat content, thus less than half the calories of normal margarine which contains about 80% fat. Typical diet margarine products which contain 60% or more of an aqueous phase have been the source of considerable technical difficulty and investigation.
The art is replete with prior art attempts to provide low-fat butter or margarine substitutes. Among these is U.S. Pat. No. 3,457,086 to Josefowicz et al, which teaches the production of a protein-free spread which contains as low as 35% fat. The patent states that the observance of specified conditions is necessary to maintain the emulsion in the water-in-oil form. Unfortunately, products of this type tend to have a watery flavor because of their high water content and the absence of milk proteins which help impart the desirable butter-like taste of margarine or butter, but which cannot be tolerated in the product because of their emulsion destabilizing effect. Moreover, the high water content tends to make emulsions of this type rapidly break down on hot foods, tending to make foods like toast become soggy and unappetizing. Moreover, while some consumers have found it convenient to buy large quantities of margarine or butter at sale prices and then freeze them, low-fat spreads prepared by that and similar processes cannot tolerate freezing. Upon thawing, the emulsion breaks down with consequential release of its water phase.
Typically, low-fat spreads of the type disclosed by Josefowicz et al, cited above and Spitzer et al in U.S. Pat. No. 3,360,377, result in very tender emulsions when desirably low fat contents, on the order of about 40%, are employed. For example, Spitzer et al, which discloses examples A-J of different suitable margarine oils, D and E being randomized coconut oil and coconut oil blends, emphasize the need for rapid cooling after homogenization to maintain emulsion stability, especially when lower-fat contents are employed. Spitzer et al disclose that 20% to about 55% oleaginous ingredients can be formed into an emulsion suitable for a margarine substitute when certain procedural constraints are observed. For example, in forming the emulsion, it is necessary to first form a coarse emulsion at a temperature within the range of around 80.degree. to 140.degree. F. and then cool prior to forming a fine emulsion in a colloid mill at a temperature within the range of around 73.degree. to 113.degree. F. The temperature at which the chilled emulsion assumes an appropriate consistency is disclosed as generally within the range of from around 50.degree. to 72.degree. F., for example 59.degree. F. These emulsions will not tolerate cooling in conventional scraped surface chilling processors at temperatures below 50.degree. F. Processing at temperatures of around 50.degree. F. or below results in breakdown of the emulsion. And, at temperatures in the 50.degree. to 60.degree. F. range, the emulsion becomes extremely stiff and heavy. The emulsions become so stiff and heavy that they often present problems of flow into the packaging container or physically exude free moisture from the mass. Further, like the products produced by Josefowicz et al, the emulsions of Spitzer et al cannot tolerate the presence of milk protein as conventionally employed in margarines and require elevated levels of emulsifiers, especially at low fat contents.
Further exemplary of prior art low-fat margarine processing is U.S. Pat. No. 3,889,005 to Brammer et al. According to that disclosure, an emulsifier system consisting essentially of saturated fatty acid partial glycerides and unsaturated fatty acid partial glycerides is said to improve emulsion stability. However, evidence that low temperature working in a scraped-surface chilling process cannot be achieved is the statement in the examples that the product is worked and packed at 20.degree. C. (68.degree. F.). At these temperatures, the crystal form of the solid fat will be predominantly in the beta form which results in large crystals, on the order of 25 to 50 microns. Apparently, these large crystals of fat and the high content of water in globules of 3-5 microns, together create a stiffness at low temperatures in the chilled processor which ruptures the fat boundaries separating the water globules and causes emulsion breakdown. This is typical of known low-fat margarines based on water-in-oil emulsions.
A further deficiency of many diet margarine products is that they cannot retain emulsion stability when subjected to freezing temperatures and then thawed. Typically, exposure to freezing temperatures and subsequent thawing results in coalescence of water droplets due to the expansion of the dispersed water during ice crystal formation and subsequent contraction upon thawing. The problem is especially acute in diet margarines because the water usually predominates over the fat in concentration, leaving the fat highly stretched out and incapable of maintaining the water in dispersed form as it stretches and then contracts during the freeze/thaw cycle. Some diet margarines have overcome this deficiency in freeze/thaw performance by the addition of gelatins and gums to the dispersed water phase. Such diet margarines still, however, require scraped-surface cooling at temperatures higher than 50.degree. F., have poor stability at elevated temperatures, and have an undesirable mouthfeel.
In an effort to overcome the problems caused by the presence of protein and low fat content in low-fat spreads, Bodor et al disclose in U.S. Pat. No. 4,103,037 the use of a gelling agent, such as gelatin, having a melting point sufficiently high to withstand room temperature yet low enough to allow it to melt in the mouth. This gelling agent ties up all available water into minute, solid particles which are dispersed throughout a continuous fat phase. These multiple particles contain the water soluble flavors and salt, and diminish the flavor impact of these components.
In further evidence of the poor stability of the currently available low-fat spreads based upon water-in-oil emulsions, are several more recent patents which employ oil-in-water emulsions. Among these are U.S. Pat. No. 4,238,520 to Miller et al, which discloses an oil-in-water emulsion having stably dispersed therein about 20% to 40% fat and preferably employs from about 2% to 5% of a lipoidal emulsifier and 0.5% to 3.25% of a thickening agent. In another approach, Bosco et al, U.S. Pat. No. 4,279,941 disclose a spread based upon an oil-in-water emulsion containing from 5% to 40% fat and employing hydrophilic emulsifiers in combination with stabilizing agents and fats having specified SFI profiles. While products of the types described in these patents do have advantages in terms of emulsion stability and the ability to employ protein, they are a departure from more typical margarine technology based upon water-in-oil emulsions, and thus require significantly different processing.
There remains a need for a water-in-oil based low-fat spread which has improved stability and provides an effective substitute for conventional margarine and butter under a broader range of conditions of storage and use.